The invention relates to a proportional pressure regulating valve of the 3/2 directional type consisting of a valve housing which has a regulating pressure chamber and with a pressure medium sump line and with at least two diaphragm stages with defined or definable drag of which two diaphragm stages are connected with each other according to the principle of the hydraulic half bridge.
DE-C 44 26 152 describes an electromagnetic pressure regulating valve, especially for regulating the shift pressure of automatic motor vehicle transmission, which has a valve housing and control shift valve actuatable by a magnetic armature and connected therewith, which controls connections from a pressure medium intake to a consumer connection or a return flow or tank. The control shift valve is situated in a rear and in a front bearing point in the valve housing and is prestressed via an adjusting spring. With this pressure regulating valve there are throughout the service life no changes of the valve characteristic resulting from problems caused by dirty oil, since a pressure drop relative to a through flow, especially of the dirt-sensitive armature chamber, is prevented. In the inlet area on the bearing gap and on the outlet opening of the current path from the ventilation hole, the same velocity energy potential prevails.
U.S. Pat. No. 3,915,932 has further disclosed a valve which has two diaphragm stages connected according to the principle of the hydraulic half bridge and is used as volume governor for dividing a pressure medium flow in a main and an accessory flow.
The valves, already known, often have the disadvantage that they either reach a minimum working pressure near zero bar or that the leakage flow of the pressure medium is minimized to nearly zero when the working pressure is minimal.
The problem on which this invention is based is to provide a proportional pressure regulating valve, especially for the regulation of shift pressure in automatic motor vehicle transmissions, in which the minimal working pressure is almost zero and the leakage flow of the pressure medium in the end position of the control shift valve is minimized to almost zero with minimal working pressure and which makes possible an adaptation of the flow properties of the valve to the conditions existing during utilization.
The aforementioned problem is solved by the present invention.
The pressure regulating valve is designed as connected throttle or diaphragm system (hereinafter the expression diaphragm will be used to mean throttle or diaphragm). The connected diaphragm system consists of two mechanically of hydraulically connected regulating diaphragms. The regulating diaphragms are according to the principle of the hydraulic half bridge. Before the two regulating diaphragms can be front-mounted a fixed diaphragm. This connected diaphragm system has three connections: a pressure medium supply line (connection P), a working pressure line to the consumer (connection A) and a pressure medium sump line to the pressure medium sump (connection T). The connection P is situated on the inlet side before the first regulating diaphragm or fixed diaphragm, the connection A is situated, e.g. between the two regulating diaphragms and the connection T is located on the outlet side behind the second regulating diaphragm. Each one of the diaphragms constitutes a drag. The two regulating diaphragms are at the same time adjustable drags. The operating principle of said pressure regulated valve works similarly to the one of an electric voltage divider with two connected adjustable slide resistances or with a front-mounted fixed resistance and two connected adjustable slide resistances. Each one of the diaphragms produces a certain pressure drop. On the input side of the first regulating diaphragm or of the fixed diaphragm supply pressure prevails, while on the output side, after the second regulating diaphragm, ambient pressure prevails. The pressure between the two regulating diaphragms is adjustable, according to the opening of the diaphragms, between ambient pressure and supply pressure. At the same time, the two regulating diaphragms form inlet and outlet openings of a pressure regulating chamber and each has a sealing element for opening and closing the diaphragms. According to the invention, the sealing element of the inlet diaphragm is designed as ball, or calotte, or truncated cone, or cylinder and/or of the sealing element of the outlet diaphragm as ball, calotte, or truncated cone, or cylinder, i.e. on one hand, a sealing element in the inlet or outlet is designed as ball, calotte, truncated cone, or cylinder. On the other hand, both sealing elements can be designed as ball, calofte, or truncated cone, or cylinder, it being possible for both sealing elements to have either the same or different shape. The inflowing and outflowing characteristic of both regulating diaphragms can thus be advantageously adjusted as best as possible to the existing condition of use of the valve. The type, e.g. of each separate diaphragm as seat or shift valve and thus the shape of the sealing surface, the same as the pressure intensification through each diaphragm, is at the same time individually adjustable.
Both regulating diaphragms are connected by a control shift valve. The diaphragms, especially the sealing elements, do not have to be rigidly or integrally connected with the control shift valve, but can also be separately designed and loosely abut on the control shift valve, the contact force being produced in the pressure medium flow by the drag of a loose diaphragm. By moving the control shift valve in one direction, the cross section of the inlet diaphragm is enlarged and that of the outlet diaphragm is simultaneously reduced. When the control shift valve moves in opposite direction, the cross sections change in inverse manner. This corresponds to the operation principle of a hydraulic half bridge. Depending on the configuration of the connection, positions of the control shift valve can result in which one diaphragm is already fully open while the other still is not fully closed (negative overlapping of the leading edges). In a possible condition of operation, the inlet diaphragm is already completely open and the outlet diaphragm still not fully closed. In this condition of operation, the system of the two connected regulating diaphragms becomes reduced to a system having fixed inlet diaphragm and regulatable outlet diaphragm.
In a system of two connected regulating diaphragms with front-mounted fixed diaphragm, if the drag of the inlet regulating diaphragm is clearly less than that of the front-mounted fixed diaphragm, then the inlet regulating diaphragm for the self-adjusting regulating pressure is no longer important. The system comprised of one front-mounted fixed diaphragm with two consecutive connected regulating diaphragms becomes reduced in this operation condition to a system with fixed inlet diaphragm and regulatable outlet diaphragm. According to the present state of the art, by means of one such reduced system, e.g. mechanical shift pressure for transmission control are regulated. This means that in this operation condition, it is possible to apply the experience acquired over the years with conventional seat valves.
Compared to the system having one regulating diaphragm and one fixed diaphragm, the system having two connected regulating diaphragms has the advantage that when the outlet diaphragm is fully open the through flow is not maximal as in the system of fixed and regulating diaphragms but is minimized to zero by the sealing element of the inlet regulating diaphragm. The same also applies to the case of additionally front-mounted fixed diaphragm. The operation condition xe2x80x9cfully open outlet diaphragmxe2x80x9d corresponds in both systems and in the reduced system with fixed inlet diaphragm and regulatable outlet diaphragm to the minimal regulating pressure. In the system having two connected regulating diaphragmsxe2x80x94with or without front-mounted fixed diaphragmxe2x80x94said lowest, adjustable regulating pressure is minimized by blocking the inlet to ambient pressure across the outlet, while in the system comprised of fixed and regulating diaphragms a final residual pressure remains due to the hydrodynamic effects. The medium through flow is higher in the system comprised of fixed and regulating diaphragms. This results in higher power losses compared to the system having two connected regulating diaphragms. One other advantage is that as a consequence of the low maximum through flow, the pump for preparing the supply pressure can be given smaller dimensions.
According to a first design of the invention, the pressure regulating valve is constructed as a system of two variable diaphragm stages mechanically or hydraulically connected. This advantageously stands out by a simple, economical construction.
In an advantageous development of the invention, the valve is constructed as a system of three diaphragm stages having one first pressure-side, fixed diaphragm stage and two connected variable diaphragm stages whereby more possibilities exist for adjustment of the flow properties than in the above mentioned design having only two variable diaphragm stages.
This pressure regulating valve, according to the invention, is advantageously used for regulating the hydraulic pressure for actuating transmission shifts.
In an advantageous development of the invention, two variable diaphragm stages are lodged in one part. The inlet diaphragm in the regulating pressure chamber is shown in the shape of a hole through a valve housing that forms an intake which can be covered with a sealing element. The outlet diaphragm is designed in the form of a seat valve where an axial wall surface of the valve housing covers a sealing or front surface of a sealing element, particularly of an armature rod. A stud-shaped control shift valve, which joins up in axial direction with the armature rod, can push out from its seat the sealing element of the inlet diaphragm. The control shift valve connects the two diaphragms, on one hand, by establishing the cross section of the inlet diaphragm by covering the intake surface with the sealing element and, on the other, by determining the surface of the outlet diaphragm by the spacing between the axial wall surface and the front face. When the outlet is closed, the front sealing surface of the armature rod abuts on the wall surface of the valve housing. The stud-shaped control shift valve at the same time pushes the sealing element of the inlet diaphragm out of its seat in the intake. The intake in the pressure regulating chamber is completely released in this position. Due to the axial movement of the control shift valve, the outlet diaphragm opens and causes a pressure drop in the pressure regulating chamber and thus in the working line. When the outlet cross section is further opened, the stud-shaped control shift valve is drawn further back. The sealing element of the inlet diaphragm thus approaches the intake and the effective intake cross section diminishes. When the outlet is almost completely open the intake is fully blocked. The pressure regulating chamber is then completely separated from the intake and an ambient pressure appears.
The sealing element does not have to be integrally connected with the control shift valve or the armature rod, i.e. the parts designed with two or more pieces. The flow or the pressure of the pressure medium allows it to abut on the control shift valve and follows up the control shift valve when it retracts. For lodging the sealing element, especially when it is not integrally connected with the control shift valve, a cage is advantageously provided which can also be used for targeted setting of the inflow characteristic.
Since the intake opening forms one part of the front surface of a cylindrical valve chamber, the force acting upon said surface has an axial component so that a hydrostatic cohesion has to be overcome to open said intake by axial displacement of the control shift valve and thus removal of the sealing element from its seat in the intake opening under different pressure in the pressure regulating chamber and intake. The cohesion results from the difference of the medium pressure in the intake and the pressure regulating chamber multiplied by the surface of the intake opening. Therefore, the intake opening is not given too large dimension in order to obtain an acceptable valve characteristic. When the valve is open the axial force upon the armature results as sum of the product from a medium value of the pressure in the pressure regulating chamber, which approximately corresponds to the working pressure in the consumer, and the free armature surface (full armature surface minus cross sectional surface of the control shift valve) and by the force produced by the back pressure on the sealing element.
The sealing element is advantageously designed in one piece with the control shift valve.
In a technical variant both mechanically connected diaphragms are regulated by a shift valve which projects through both diaphragm openings and over its axial extension has a double-sided cone with a tapering in its center. On its axially outer ends the cross section of the control shift valve increases in a manner such that it can completely seal the diaphragm openings. By movement in one or other axial direction it thus seals the inlet or outlet diaphragm.
In an advantageous development of this technical variant of the invention, a fixed diaphragm is mounted in front of the two mechanically connected diaphragms.
The pressure regulating valve is preferably magnetically actuated. The displacement force of said pressure regulating valve is at the same time the force which an electromagnet exerts on the induced, magnetic torque of a soft-iron armature. The soft-iron armature is advantageously pressed on the armature rod.
As technical variant, the pressure regulating valve can also be actuated piezo-electrically or pneumatically.
In another advantageous development of the invention, three diaphragms are lodged in a discrete part. The three diaphragms are composed of one fixed diaphragm on the intake side and two connected regulating diaphragms. The fixed diaphragm on the intake side can here be designed as front-mounted diaphragm but also as throttle in the shape of one or more holes. The connected regulating diaphragms form the inlet and outlet of a regulating pressure chamber. The regulated inlet diaphragm is shown by at least one radial intake hole through a valve housing interacting with a control shift valve which extends partially into the cylindrical, hollow pressure regulating chamber. The control shift valve is axially movable over a certain length within the pressure regulating chamber. The control shift valve consists of one sleeve which can accurately fitting slide in the cylindrical pressure regulating chamber and at least one preferably web-shaped connecting piece to a front surface of an armature rod. The front surface is larger than the axial cross sectional surface of the pressure regulating chamber. The cross sectional surface of the inlet hole(s) can be sealed to any extent desired by the surface of the sleeve. The axial outer wall of the sleeve constitutes at the same time the leading edge of the inlet diaphragm wherein the latter acts as control shift valve. The outlet diaphragm is formed by a seat valve in which an axial wall surface of the valve housing covers the front surface of the armature rod. The web-shaped connecting piece constitutes the mechanical connection between the leading edges. When the outlet is closed, the front surface of the armature rod abuts on the wall surface of the valve housing. The sleeve projects here into the cylindrical pressure regulating chamber far enough so that the radial intake hole(s) be located between sleeve and front surface of the armature rod. The intake hole(s) is (are) completely released in this position. By axial movement of the control shift valve, the outlet diaphragm opens and causes a pressure drop in the pressure regulating chamber and thus in the working line. When the outlet cross section is further opened, the inlet leading edge begins to strike over the cross section of the radial intake hole(s). When the outlet is almost completely open, the intake hole(s) becomes (become) completely blocked. The pressure regulating chamber is then completely separated from the intake and ambient pressure appears there. In this development of the invention the armature rod and the control shift valve comprised of the web-shaped connecting piece and the sleeve are advantageously designed in one piece. The production as rotary part recommends itself wherein the end forming the control shift valve is turned off as hollow cylinder and subsequently a milling work cycle across the axis of rotation leaves residually as webs two axially extending hollow cylinder segments which constitute the connecting piece between armature rod and sleeve. Since the inlet opening(s) is (are) situated on the surface of one cylindrical valve chamber, the force acting upon said surface has no axial component so that for opening said inlet (said inlets) by axial displacement of the sleeve under different pressure in the pressure regulating chamber and intake, no hydrostatic cohesions have to be overcome. The axial force upon the armature results as product of a medium value of the pressure in the pressure regulating chamber, which nearly corresponds to the working pressure in the consumer, and the full armature surface (free armature surface plus cross sectional surface of the connecting piece).
The sleeve connected via the web-shaped connecting piece with the armature rod, by adequate matching of material, can be directly lodged in the valve housing as hydraulic-side bearing.
The armature rod and the control shift valve are preferably designed in one piece.
The inlet regulating diaphragm preferably has in the valve housing several radial intake holes which are connected via an annular duct with the front-mounted, fixed diaphragm.
In an advantageous embodiment of the invention, one sealing surface is provided on one front side of the armature rod, said sealing surface interacting with a corresponding sealing surface on the valve housing and thus making possible a flat-seat sealing with the best sealing properties.
In one other design, it is now proposed frusto conically to design the area between the front surface of the armature rod designed as sealing surface and the control shift valve. Thus are advantageously combined by the truncated cone the good sealing properties of a flat seat with a favorable, namely, as low as possible, design of the pressure booster, the base of the truncated cone being disposed on the front surface of the armature rod.